1. Field of the Invention
The invention is generally related to inspection of recirculating steam generators and in particular to retrieval of loose parts in the annular space around the tube bundle and within a shallow penetration into the tube bundle proper.
2. General Background
Recirculating steam generators have a history of discoveries of loose parts on the secondary side face of the tubesheet during inspection. Their wide tube lanes capture or collect large pieces of debris such as machine chips, bolts, and pieces of welding wire. It is desirable that such debris be removed due to its potentially damaging effect on the tube bundle. Because access holes in the outer steam generator shell are often two inches in diameter, with little room to maneuver both inside and outside the shell hole, inspection and parts retrieval is difficult. Previous attempts at removal of parts include the use of robotic devices and fiberoptics along with a hook or prod. Robotics present limitations relative to size and maneuverability once inside the steam generator since the annular space between the tube bundle and shell inner wall is as little as four inches. Fiberoptics and hooks or prods have been inserted independently of each other without suitable means of guidance, synchronization, or articulation. It can be seen that a need exists for a more efficient means of inspecting and retrieving loose parts in steam generators.